This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. There are several major diseases that men may get as they get older. In the United States, Heart disease is the most common cause of death in men age 45 and older, followed by cancer. Prostate cancer is the most commonly occurring major non-skin cancer in men, followed by lung cancer and cancers of the colon and rectum. If these diseases could be prevented, men could expect to live longer and healthier lives. This study will try to find out if taking selenium and/or vitamin E will reduce the risk of developing prostate cancer, lung and colon cancer, all cancers combined and heart disease. Three studies have suggested that taking selenium and vitamin E in the diet may offer some protection against cancer of the prostate, lung and colon. SELECT will include about 32,400 men from centers throughout the United States to investigate this further and possibly help improve the health of men age 55 and older (or age 50 and older for African American men). Men will be followed in the study for 7-12 years.